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The growing need for high-performance folded cascode CMOS OTAs in various fields, such as electronics and communications, requires them to operate with wide bandwidth, high voltage gain, compact devices, and low power consumption. Recent research indicates that implementing the water cycle algorithm (WCA) can greatly improve the performance of the folded cascode CMOS operational transconductance amplifier (OTA). This is due to the WCA's ability to perform both global search and local exploration efficiently. Notably, the OTA in question is constructed using 0.18µm TSMC technology and operates with a voltage supply of ±1.8V. The results of the simulation were collected using PSPICE software (version 17.4). These design solutions demonstrate exceptional efficiency, delivering significant amplification, high frequency, and minimal power usage. In addition, the paper demonstrates the implementation and simulation outcomes of a folded cascode CMOS operational transconductance amplifier utilizing the water cycle algorithm, MATLAB was employed for this purpose. Using WCA in the design of an OTA for folded cascode CMOS OTA results in significant improvements in performance metrics. Experiences a significant increase in voltage gain, with an increase in gain bandwidth by a factor of five compared to the algorithm-free design. In addition, power consumption is reduced by 15.5%, and the common mode rejection ratio is improved by 15.18% compared to the non-WCA folded cascode CMOS OTA design. The results highlight the effectiveness of the WCA technique as a powerful optimization strategy to improve the performance of folded cascode CMOS OTA. [ABSTRACT FROM AUTHOR]

Industrial processes of time delayed integrating type require sophisticated control methods because of their non-self-regulating nature. Literature presents fractional order controllers as possible solution to this problem and there is scope for further enhancing the performance of the existing solutions. Though fractional order controllers are capable of outperforming their integer order counterparts, it is evident in literature that the former controller designs are complex and hence analytical tuning procedures for the same are scarce. Hence, this paper presents a novel predictive strategy for time-delayed integrating processes based on two fractional-order tilt-derivative (FOT $^{\alpha} \text{D}^{1-\alpha }$ ) controllers. These controllers are analytically designed with only two tunable parameters. These tuneables are computed using gain- and phase-margin specifications. In contrast to the previous methods, the presented scheme is more capable of eliminating input-load disturbances without adding complexity in terms of tunable parameters. In addition to the investigations carried out using three difficult benchmark plant models, the present design is also experimentally validated using a two-tank level control system to vindicate its efficacy. Through robust stability analysis, it is shown that the suggested strategy is capable of achieving stable closed-loop responses amid upto 50% perturbation in plant parameters.

This paper provides a detailed exploration of CMOS operational amplifiers (Op-Amps) aimed at enhancing understanding of their development, design, and application. To achieve this, a comprehensive examination of the common characteristics, parameters, and bibliographic reviews of Op-Amps, distinguishing among various chosen operational amplifiers. A comprehensive bibliographic review of the operational amplifier's keywords between 2008 and 2018 has also been conducted. A bibliometric analysis of 4997 documents from the Web of Science (WOS) Collection is conducted using VOSviewer software. Furthermore, an analysis and comparison of these Op-Amps across functional aspects relevant to industrial and biomedical applications, emphasising the salient characteristics of each technique. After the survey, a novel Op-Amp design is proposed, incorporating a differential amplifier at the first stage, along with a compensating capacitor and a high gain stage. The biasing circuitry is replaced with an active load resistor (MOS transistor), simplifying layout design, and reducing the amplifier's area and power consumption compared to traditional two-stage designs. The power source for this design is 3.3 V. This designed operational amplifier achieved a gain of 62.9449 dB, a high CMRR of 92.8079 dB, and a unity gain bandwidth of 33 MHz, and the optimised layout area is 0.001476 μm2. The proposed circuit was designed and simulated utilising the Cadence Virtuoso 180 nm CMOS process. The simulation results show that the desired criteria have been met. Additionally, the challenges and future possibilities in analog circuits, laying the groundwork for research in both analogue and digital circuits to tackle complex real-world issues have been addressed.

Interactive two-input two-output processes with time delays (TITOTD) generally have strong loop interactions and exhibit complex response characteristics. This study develops an alternative method to rapidly and graphically tune optimal and robust decentralized PID (ORDPID) controllers to stabilize TITOTD systems using the designer-defined frequency domain robustness specifications. To eliminate loop interactions, a decoupler is initially used to decompose the TITOTD system, so two independent time-delayed single-input single-output subsystems (SISOTD) are derived. To guarantee the frequency domain specifications for a controlled system in terms of gain margin (GM) and phase margin (PM), each SISOTD subsystem is incorporated with a gain-phase margin tester (GPMT). Without approximating the delay terms and reducing the orders of the SISOTD processes, the stability equation method determines the GM and PM-associated boundaries in the parameter plane. For each decoupled SISOTD process, a GM and PM specification-oriented region (GPMSOR) that encloses all admissible robust decentralized PID (RDPID) controllers is graphically characterized in the parameter plane. Two independent ORDPID controllers are searched within the determined GPMSORs by minimizing the IAE or the ISE performance index. For verification, the determined ORDPID controllers are evaluated using the original TITOTD processes with four simulation examples from the literature.

The controllable intensified process has received immense attention from researchers in order to deliver the benefit of process intensification to be operated in a desired way to provide a more sustainable process toward reduction of environmental impact and improvement of intrinsic safety and process efficiency. Despite numerous studies on gain and phase margin approach on conventional process systems, it is yet to be tested on intensified systems as evidenced by the lack of available literature, to improve the controller performance and robustness. Thus, this paper proposed the exact gain and phase margin (EGPM) through analytical method to develop suitable controller design for intensified system using Proportional-Integral-Derivative (PID) controller formulation, and it was compared to conventional Direct Synthesis methods (DS), Internal Model Control (IMC), and Industrial IMC method in terms of the performance and stability analysis. Simulation results showed that EGPM method provides good setpoint tracking and disturbance rejection as compared to DS, IMC, and Industrial IMC while retaining overall performance stability as time delay increases. The Bode Stability Criterion was used to determine the stability of the open-loop transfer function of each method and the result demonstrated decrease in stability as time delay increases for controllers designed using DS, IMC, and Industrial IMC, and hence control performance degrades. However, the proposed EGPM controller maintains the overall robustness and control performance throughout the increase of time delay and outperform other controller design methods at higher time delay with ± 20 % uncertainty test. Additionally, the proposed EGPM controller design method provides overall superior control performance with lower overshoot and shorter rise time compared to other controllers when process time constant is smaller in magnitude ( τ p = 0.01 and 0.1 ) than the instrumentation element, which is one of the major concerns during the design of intensified controllers, resulting overall system with a higher order. The desired selection of gain margin and phase margin were suggested at 2.5 to 4 and 60 °–70 ∘ , respectively, for a wide range of control conditions for intensified processes where higher instrumentation dynamic would be possible to achieve robust control as well. The proposed EGPM method controller is thought to be a more reliable design strategy for maintaining the overall robustness and performance of higher order and complex systems that are highly affected by time delay and high dynamic response of intensified processes. [ABSTRACT FROM AUTHOR]

This paper proposes a simplified and analytical method for designing fractional order lead compensator (FOLC). In the proposed method, the structure of fractional order lead compensator considered is more generalized. The fractional operator of the FOLC is approximated to its equivalent rational form using binomial expansion to lower the computation complexity of the designing approach. Then, steady-state gain, gain cross over frequency and phase margin are used as the design specifications of the FOLC. The proposed method also considers the magnitude and phase of the plant to be controlled. Phase margin criteria ensure the stability of the designed compensator. The compensator is designed strictly adhering to gain and phase margin criteria. The proposed methodology is validated with four different illustrative examples through simulation. Integral absolute error (IAE) and integral square error (ISE) are considered as the performance indices. The simulation results demonstrate that the proposed scheme gives a better transient response, IAE, and ISE as compared to the existing FOLC design techniques. [ABSTRACT FROM AUTHOR]

Local hyperthermia is one of the most prevalent thermal therapies for cancerous tumors, near the skin surface or natural body orifices. Due to the requisiteness of temperature control during local hyperthermia, first, the heat conduction process during the mentioned therapy is analytically modeled via a fractional-order transfer function with time delay. Since the influence of the heat source and the patient`s physiological reaction may vary the patient body temperature and affect all of the model parameters, robust control of temperature during the treatment is necessary. Hereupon, this study suggests a novel robustness criterion to achieve the phase margin invariance despite concurrent uncertainty on different parameters of the process model. Afterward, an analytical method is presented to tune a Fractional-Order Proportional-Integral-Derivative (FO-PID) controller for desirably adjusting the values of phase margin and gaining crossover frequency, such that the proposed robustness feature is also satisfied. Finally, a numerical simulation is presented to evaluate the efficiency of the paper`s achievements, using practical parameters.

The purpose of this report is to explain the design and implementation process of a PID controller with a lead network to control the tilt angle of an aerodynamic rocker. For this, the mathematical model of the plant was built and the physical and electrical parameters that characterize the plant were identified experimentally. By linearizing the model around a defined operating point, the transfer function of the system was obtained, which was validated by means of simulations in MATLAB®-Simulink. With this, the PID controller and the lead network were designed considering the performance and robustness requirements. Subsequently, the plant was physically built, and the control system was implemented in a Microchip® brand PIC18 microcontroller. Finally, tests were carried out on the physical implementation to verify the performance and robustness attained. As a result, a controller was obtained whose implementation is fast, has a good follow-up to a wide range of references, rejects disturbances, and is robust to changes in the plant. It is concluded that the implementation in the proposed microcontroller was successful and other researchers are invited to experiment with this project in different ways. [ABSTRACT FROM AUTHOR]

Versatile and often used operational amplifier (op-amp) architecture, the two-stage op-amp is appropriate for a variety of analogue circuits and applications, including high-precision amplification and signal conditioning. It offers high gain, which is essential, good frequency response and stability, especially when used with cutting-edge hardware like Complementary Metal-Oxide Semiconductor (CMOS). For high-speed applications that require more bandwidth, this can be a drawback. The CMOS op-amp circuit may produce a consistent output dc offset voltage if improperly built. Modeling of transistors has become an important design procedure to obtain a better op-amp for greater performances. Here we proposed an op-amp compensated with miller capacitance to gain high parametric values such as Gain (AV), unity-gain frequency, Power dissipation, a supply voltage of 1.2V, Slew Rate (SR), Phase margin (PM). The op-amp is simulated using OrCAD Capture to obtain the improved stability and enhance the parameters. The proposed op-amp can be used in high-speed applications and signal conditioning. [ABSTRACT FROM AUTHOR]

In view of the blindness of the trial-and-error method in the design of DC-DC transform compensation network and the complexity of theoretical analysis, based on the state space average method, this study takes Buck as an example to model the DC-DC transformation system. Under the condition that the amplitude margin and phase margin are satisfied, the relationship between the compensation network kp, ki and the system parameter duty ratio D, inductance L and capacitance C is derived, and on this basis, an engineering approximation method is proposed. The proposed method is verified by PSIM simulation and a prototype platform based on DSP. The results show that the results obtained by this engineering approximation method are basically consistent with the theoretical analysis method, that is, the traditional control method, no matter in the case of voltage single closed loop or in the case of voltage outer loop and current inner loop. This engineering approximation method avoids the blindness of trial and error and the complexity of traditional control methods, which is the complexity of traditional control methods, and provides a quick method and idea for the rapid design of compensation networks in actual projects. [ABSTRACT FROM AUTHOR]

Diffusion processes, as fundamental mechanisms for particle movement in systems with different concentrations, are used to describe many real-world physical, chemical, biological, engineering, economic and social phenomena. A diffusion process can be modelled via a fractional-order transfer function with time-delay, where its parameters may be affected by circumstance. Hereupon, this study proposes a pioneer robustness indicator to achieve the phase margin invariance regardless of concurrent uncertainty on different parameters of a diffusion process. Afterwards, an analytical procedure is suggested to tune a Fractional-Order Proportional-Integral-Derivative (FO-PID) controller for a diffusion process, to favourably regulate the values of gain crossover frequency and phase margin, such that the proposed robustness criterion is met. Moreover, the solvability of the problem is analytically investigated. Finally, a numerical simulation on robust temperature control during magnetic local hyperthermia, i.e. a common method to treat cancerous tumours, is presented to validate the efficiency of the paper achievements. [ABSTRACT FROM AUTHOR]

The ports of a three-phase voltage source converter have multiple frequency electrical parameters, which makes HVDC systems with these converters present multiple input multiple output (MIMO) characteristics. The generalized Nyquist criterion of the MIMO model is often used to analyze the system stability. However, this model is more difficult to obtain than the single-input single-output (SISO) model, and the stability margin and the oscillation frequency band are difficult to capture. To solve these problems, this paper took the two-terminal HVDC transmission system as the research object to derive a SISO model that can be measured by a port. Moreover, this study also proposed a method for analyzing the system stability through envelope SISO open-loop gains. Finally, the key port and parameters affecting the system stability were analyzed according to the stability margin, which provided theoretical support for the design of the system parameters. The established model and the proposed analysis method were verified in a MATLAB/Simulink simulation model.

Proportional-integral (PI) control is widely used in turbofan-engine control, while first-order linear active disturbance rejection control (FOLADRC) is a possible approach to update it. This paper investigates FOLADRC. In methodology, it proposes a new block diagram of FOLADRC, which shows that FOLADRC can be viewed as a PI controller, a low-pass feedback filter, and a pre-filter. The low-pass filter helps to reject high-frequency measurement noise, while the pre-filter can attenuate overshoot in step response. In simulation, 14 published linearized model matrices of NASA's CMAPSS-1 90k engine model are used to verify the above theory. Simulations show one FOLADRC controller can be simultaneously used for the 14 linear models and guarantee that all the 14 low-pressure turbine speed control loops have enough phase margin and no overshoot. Thus, replacing several PI controllers with one FOLADRC controller is possible, and FOLADRC can be used to simplify the control system design of turbofan engines. [ABSTRACT FROM AUTHOR]

This article presents a method for calculating all the proportional–integral/proportional–derivative controllers with a low-pass filter of a given order, which satisfy gain–phase margins and sensitivity (or complementary sensitivity) specifications. The method is explicit and requires solving a set of a polynomial and two linear equations. It is shown how to extend the method to design all the proportional–integral–derivative or cascaded controllers with a low-pass filter assuming that a minimum value of one of the controller components is given. [ABSTRACT FROM AUTHOR]

This article deals with the computation of robustly performing Proportional-Integral (PI) controllers for interval plants, where the performance measures are represented by the worst-case Gain Margin (GM) and Phase Margin (PM) specifications, in the event of multiple Phase Crossover Frequencies (PCFs) and/or Gain Crossover Frequencies (GCFs). The multiplicity of PCFs and GCFs poses a considerable complication in frequency-domain control design methods. The paper is a continuation of the authors’ previous work that applied the robust PI controller design approach to a Continuous Stirred Tank Reactor (CSTR). This preceding application represented the system with a single PCF and a single GCF, but the current article focuses on a case of multiple PCFs and GCFs. The determination of a robust performance region in the P-I plane is based on the stability/performance boundary locus method and the sixteen plant theorem. In the illustrative example, a robust performance region is obtained for an experimental oblique wing aircraft that is mathematically modeled as the unstable interval plant. The direct application of the method results in the (pseudo-)GM and (pseudo-)PM regions that “illogically” protrude from the stability region. Consequently, a deeper analysis of the selected points in the P-I plane shows that the calculated GM and PM boundary loci are related to the numerically correct values, but that the results may be misleading, especially for the loci outside the stability region, due to the multiplicity of the PCFs and GCFs. Nevertheless, the example eventually shows that the important parts of the GM and PM regions, i.e., the parts that have an impact on the final robust performance region, are valid. Thus, the method is applicable even to unstable interval plants and to the control loops with multiple PCFs and GCFs.

In this paper, a low voltage bandgap reference circuit has been proposed. The introduction of a modified beta multiplier bias circuit decreased the mismatch caused by the PMOS transistors opamp contribution. By shifting the fixed resistors to the NMOSs drain side, the beta multiplier bias minimised threshold mismatch between the two NMOS transistors. A 200-point MC simulation showed a 0.9 mV standard deviation, with a 0.34% accuracy. The simulated temperature coefficient was 64 ppm/0C. The proposed circuit consumed 5.04 µW of power from a 0.45 V power supply voltage. A prototype was implemented in 65 nm CMOS technology occupying a 2888 µm2 silicon area, with the nominal value of the reference at 261 mV. [ABSTRACT FROM AUTHOR]

In this paper, a gain enhanced transconductance amplifier having high bandwidth and improved phase margin has been proposed. Miller compensation technique, using a series connected capacitor and resistor branch has been utilized to improve the phase margin of adaptively-biased cross-coupled high gain transconductance amplifier (proposed OTA-I). Further, gate compensation resistor is utilized to achieve bandwidth extension (proposed OTA-II). This proposed structure offers improvement in phase margin and bandwidth without increasing the power consumption or supply voltage requirement, while maintaining DC gain and linear range of the gain enhanced transconductance amplifier. The simulation results have been carried out in EldoSpice using TSMC based level 53, 0.18 µm CMOS technology with ± 0.6V supply voltage. These results show that for peaking free response in proposed OTA-II, phase margin of 59.40° and bandwidth of 33.31MHz can be achieved compared to values of 51.92° and 16.10MHz in conventional OTA. Monte Carlo and temperature analysis demonstrate robustness of the proposed circuit against process and temperature variations. [ABSTRACT FROM AUTHOR]

In this paper, optimum transistor sizing of CMOS differential amplifier using tunicate swarm algorithm (TSA) is proposed. The designing of CMOS differential amplifier is activated to determine the best feasible design parameter values. This work proposes the optimized values of various parameters of a CMOS differential amplifier for better performance. TSA is chosen to optimize the circuit area. TSA has the ability to solve complex functions, like MOS transistor size and bias current. TSA is employed to optimize the parameters of circuit design, like area, power dissipation MOS transistor size, and also used to enhance other circuit specifications, while fulfilling circuit design criteria. The design objectives of CMOS differential amplifier are considered the fitness function of TSA algorithm. Then, weight parameters of CMOS differential amplifier design are optimized using TSA. By CMOS differential amplifier using TSA algorithm, we can optimize circuit design parameters with higher probability of yielding optimal results regarding circuit area lessening, lesser power dissipation and MOS transistor sizes. The proposed method is implemented in the MATLAB platform. The proposed CMOS-DA-TSA method attains 52.01%, 50.29% and 44.30% minimum slew rate, 64.61%, 75.30% and 55.92% minimum power dissipation compared to the existing methods like CMOS-ACD-SOA, CMOS-PAI-FOPSO and CMOS-PSO-MOL, respectively. [ABSTRACT FROM AUTHOR]

This work proposes a robust tuning method for full-load pitch control by deriving new design formulae for collective Proportional Integral (PI) pitch controllers. The paper investigates the frequency domain characteristics of a full state linearized turbine model extracted from the aeroelastic simulation tool HawcStab2, and suggests a reduced order model that captures the low-frequency behaviour and may be used to derive PI tuning formulae that account for collective blade flap modes. The proposed controllers are then compared to traditional PI controllers based on a single degree of freedom (1-DOF) model of the drive-train using linearized NREL5MW and DTU10MW models. The 10 MW model is investigated in more detail through non-linear simulations in HAWC2 using wind step and turbulent wind conditions. The proposed design formulae show robust results, giving more consistent gain and phase margins than 1-DOF designs throughout the above rated wind speed region, and may be used to increase controller bandwidth while maintaining acceptable stability margins, achieving 49% and 63% reductions in standard deviation of the output power for the DTU10MW model in turbulent conditions. Statistical analysis for both controllers was also performed to investigate fatigue loading on the main shaft caused by the pitch actuation. [ABSTRACT FROM AUTHOR]

A new analytical-graphical method is proposed for computing the region of stability for proportional-integral-derivative (PID) controllers based on the Hermite–Biehler theorem. By this method, a PID controller is designed to ensure the Hurwitz stability of a time-delay system with any order of transfer function. First, the possible range of the derivative part that makes the system stable is obtained. Then, the stability region is found by applying the Hermite–Biehler theorem. It is shown that this theorem can be extended to quasi-polynomials functions in the form of ψ (ν , e ν) to find the stability region of systems with time delay under certain conditions. Using this, the proposed approach can guarantee specified gain and phase margins for time-delay systems; therefore, it is very beneficial and advantageous for the control of practical plants. Five different examples including two practical systems are studied throughout the paper to illustrate the applicability, performance, and efficiency of the proposed control approach. [ABSTRACT FROM AUTHOR]

This article proposes a dual-active-bridge control to support the fast synthetic inertial action in DC microgrids. First of all, the selection of the isolated DC/DC converter to link an energy storage system with the DC bus in a microgrid is analyzed and the advantages of the dual-active-bridge converter controlled by a single-phase shift modulation justify its selection. An active front-end can be then adapted to connect the DC bus with an AC grid. Secondly, this paper presents the design of a discrete PI controller for supporting fast synthetic inertial action. In particular, a discrete dual-active-bridge model based on the transferred power between both converter bridges, which overcomes the approximations of the output current linearization model, is proposed. Moreover, the article introduces a novel equation set to directly and dynamically tune discrete PI parameters to fulfill the design frequency specifications based on the inversion formulae method. In this way, during the voltage/power transients on the DC bus, the controller actively responds and recovers those transients within a grid fundamental cycle. Since the developed set of control equations is very simple, it can be easily implemented by a discrete control algorithm, avoiding the use of offline trial and error procedures which may lead to system instability under large load variations. Finally, the proposed control system is evaluated and validated in PLECS simulations and hardware-in-the-loop tests. [ABSTRACT FROM AUTHOR]

Generally, controllers are tuned to meet the desired time and frequency domain specifications for integer/fractional order real coefficient systems whose frequency response is symmetric about the origin of the complex frequency plane. These controllers are tuned through analytical/numerical approaches. On the contrary, the frequency responses of the complex coefficient systems are unsymmetrical, and hence tuning of controllers should consider both positive and negative frequencies. In this article, tuning of complex coefficient proportional integral derivative controller is proposed for such systems to meet the desired gain and phase margin specifications in positive and negative frequencies. For illustration, the simulation results are presented for stable, unstable, and non-minimal phase systems with the proposed tuning method. [ABSTRACT FROM AUTHOR]

Formulating a fractional-order controller and then implementing it in real-world environment is a challenging task for control professionals. Therefore, this paper proposes a simple, analytical and robust fractional-order controller synthesis scheme using Bode ideal transfer function in internal model control (IMC) paradigm. The controller acquires a PI form followed by a fractional-order integrator. The main advantage of the proposed scheme is that only two tuning parameters are required for satisfying the desired gain crossover frequency and phase margin. The properties of the proposed scheme are examined on the basis of tracking and disturbance rejection attributes. The effectiveness of the proposed method is verified through simulations of linear and nonlinear systems, and it is further experimentally validated on QUBE-Servo 2 set-up to control the velocity of DC motor. The proposed scheme exhibits satisfactory tracking and disturbance rejection performance when compared with integer-order and fractional-order PI controllers. [ABSTRACT FROM AUTHOR]

In this paper a low offset voltage; low power and high gain second stage op-amp of differential amplifier along with common source amplifier with compensated capacitor is proposed. The mathematical analysis of two-stage op-amp is elaborated and this work is compared with exiting similar work. The experimental work carried in CADENCE Virtuoso with 0 gpdk090 process technology is used to obtain 60.994 of Phase Margin, 61 dB DC gain and Offset voltage is 2mV. The M/L ratios are selected accordingly where supply voltage and load voltage are fixed at 1.8V and 12pF respectively. The parametric analysis helps, where the values are fixed to get better response. [ABSTRACT FROM AUTHOR]

Proportional-integral (PI) control is widely used in turbofan-engine control, while first-order linear active disturbance rejection control (FOLADRC) is a possible approach to update it. This paper investigates FOLADRC. In methodology, it proposes a new block diagram of FOLADRC, which shows that FOLADRC can be viewed as a PI controller, a low-pass feedback filter, and a pre-filter. The low-pass filter helps to reject high-frequency measurement noise, while the pre-filter can attenuate overshoot in step response. In simulation, 14 published linearized model matrices of NASA’s CMAPSS-1 90k engine model are used to verify the above theory. Simulations show one FOLADRC controller can be simultaneously used for the 14 linear models and guarantee that all the 14 low-pressure turbine speed control loops have enough phase margin and no overshoot. Thus, replacing several PI controllers with one FOLADRC controller is possible, and FOLADRC can be used to simplify the control system design of turbofan engines.

The present paper aims to analyze the stability of dynamic Interval Type‐2 fuzzy control systems (IT2 FCSs) with adjustable parameters by investigating the existence of limit cycles based on the describing function (DF) method. To simplify the stability analysis, the following structured procedure is described. First, to avoid complex computation, a simple architecture of the IT2 FCS using two embedded Type‐1 fuzzy control systems (T1 FCSs) is proposed. Then, the DF of IT2 FCS is obtained based on the DFs of embedded T1FCSs. Subsequently, integrating the stability equation and parameter plane approaches provides a solution to identify the limit cycle and the asymptotically stability regions. Moreover, particle swarm optimization (PSO) technique is utilized to minimize the limit cycle region. Other focus of this paper is on the stability margins analysis for robust design. For this purpose, a gain‐phase margin tester is applied to determine the minimum Gain Margin (GMmin) and Phase Margin (PMmin) when limit cycles can arise. Finally, two simulation examples are given to verify the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

In a feedback control loop, when there exists a delay in processing the control signal (often called computational delay), it is difficult to stabilize the system, particularly when the system exhibits uncertainty. To solve this problem, we proposed a new robust proportional integral control strategy for a class of uncertain systems exhibiting parametric uncertainty. A two-stage scheme is proposed in which the first stage identifies the worst plant that has the highest chance of facing instability; and in the second stage, based on the worst plant, the tuning parameters of the proportional integral controller are determined using the stability boundary locus approach under the desired closed-loop specifications of gain and phase margins. The efficiency of the proposed scheme is verified for servo and regulatory control problems. [ABSTRACT FROM AUTHOR]

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Aiming at the static unstable Hypersonic vehicle, a method for designing H∞ autopilot to satisfy gain margin and phase margin is proposed. Structured H∞ synthesis is used to synthesize the autopilot under the fixed structure. The gain margin and phase margin were constrained by using H∞ norm of the complementary of the scaled plant. The requirement for the gain margin and phase margin is represented by the distance between the open loop Nyquist curve and the circle that represents the gain margin and phase margin in the complex plane. The distance is adjusted by tuning the parameter of performance specifications automatically to reduce the conservatism of the controller. The present method is applicable to both static stable vehicle and static unstable vehicle, and a three loops acceleration tracking autopilot is design. The numerical simulations have demonstrated that the autopilot satisfys the performance specifications, gain margin and phase margin simultaneously.